1. Field of the Invention
This invention relates to non-lethal weapons and more particularly to a man-portable non-lethal pressure shield that provides both a physical shield and a pressure barrier useful for crowd control. The pressure shields may be operated independently or coordinated via wireless networking to greater effect.
2. Description of the Related Art
“Since the early 1990s there has been an increasing interest—mainly in the U.S.—in so-called non-lethal weapons (NLW) which are intended to disable equipment or personnel while avoiding or minimizing permanent and severe damage to humans. NLW are thought to provide new, additional options to apply military force under post-Cold War conditions, but they may also be used in a police context. Whereas some foresee a military revolution and “war without death,” most others predict or prescribe that NLW would just augment lethal weapons, arguing that in actual war both types would be used in sequence or in parallel. However, there may be situations other than war when having more options of applying force below the threshold of killing could help to prevent or reduce deaths, e.g. in a police context (riots, hostage-taking) or in peace-keeping operations. A range of diverse technologies has been mentioned, among them lasers for blinding, high-power microwave pulses, caustic chemicals, microbes, glus, lubricants, and computer viruses.” (Jurgen Altmann, “Acoustic Weapons—A Prospective Assessment, Science & Global Security: Volume 9, pp 165-234, 2001) Altman provides an analysis of acoutic weapons, with an emphasis on low-frequency sound, and particularly the effects on humans. Such weapons have been said to cause disorientation, nausea and pain without lasting effects. However, the possibility of serious organ damage and even death exists.
U.S. Pat. No. 5,973,999 to John T. Naff entitled “Acoustic Cannon” discloses an acoustic cannon having a plurality of acoustic sources with output ends symmetrically arranged in a planar array about a central point. Pressure pulses are generated in each acoustic source at substantially the same time. The pressure pulses exit the output ends as sonic pulses. Interaction of the sonic pulses generates a Mach disk, a non-linear shock wave that travels along an axis perpendicular to the planar array with limited radial diffusion. The Mach disk retains the intensity of the sonic pulses for a time and a distance significantly longer than that achievable from a single sonic source. The acoustic cannon is useful as a non-lethal weapon to disperse crowds or disable a hostile target. As graphically illustrated in FIG. 8, a sonic generator having a mass equivalent to the “total charge mass” equivalency of trinitrotoluene (TNT) is capable of producing a shock pulse effective to cause disorientation and debilitation, without permanent injury, over distances of from less than 10 meters to in excess of 100 meters. As illustrated in FIG. 7, attenuation increases as the frequency increases such that the maximum dominant frequency of the sonic pulses is preferably less than about 7 kHz, and more preferably, less than about 5 kHz. The sound intensity is selected to provide a desired effect to the biological target, dependent on the application. The FIG. 8 distances were computed based on a single sonic source and do not include the n2/3 factor that is obtained using multiple sources. As such, FIG. 8 illustrates the minimum over-pressure values at a given range for different values of the source strength (energy). Incorporation of the n2/3 factor for multiple sources substantially increases the effective range for a given over-pressure level.